Do you tell yourself when you don’t feel like exercising that you’re just being lazy? Actually, Harvard evolutionary biologist Daniel E. Lieberman ’86 says, we’re nearly hard-wired to avoid unnecessary exertion. In his new book, “Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding,” Lieberman explores this idea while using anthropological evidence to bust other myths and misunderstandings about exercise. The Gazette spoke with Lieberman, the Edwin M. Lerner II Professor of Biological Science, about the book and tips for getting motivated to do something as unnatural as exercise.
GAZETTE: The biggest myth you address in the book is that it’s normal to exercise. Introduce this idea.
LIEBERMAN: We live in a world where everyone knows that exercise is good for you, and yet the vast majority of people have a hard time doing it. According to government statistics, only about a quarter of Americans actually exercise in their leisure time. For me, it’s clear we’re asking people to choose to do something that’s inherently abnormal in the sense that we evolved not to do it. Humans evolved to move. We evolved to be physically active. But exercise is a special kind of physical activity. It’s voluntary physical activity for the sake of health and fitness. Until recently, nobody did that. In fact, it would be a kind of a crazy thing to do because if you’re a very active hunter-gatherer, for example, or a subsistence farmer, it wouldn’t make sense to spend any extra energy going for a needless five-mile jog in the morning. It doesn’t help you. In fact, it actually takes away precious calories from other priorities. All in all, humans have these deep-rooted instincts to avoid unnecessary physical activity, because until recently it was beneficial to avoid it. Now, we judge people as lazy if they don’t exercise. But they’re not lazy. They’re just being normal.
GAZETTE: How can people get around these natural instincts?
LIEBERMAN: Since medicalizing and commercializing exercise is obviously not working, I think we can do better if we think like evolutionary anthropologists. Here are three things people can do. The first: Don’t be mad at yourself. Don’t feel bad for not wanting to exercise, but learn to recognize these instincts so you can overcome them. When I get up in the morning to go running, it’s often cold and miserable, and I have no desire to exercise. My brain often tells me all kinds of reasons why I should put it off. I sometimes have to force myself out the door. My point here is to be compassionate about yourself and understand that those little voices in your head are normal and that all of us, even “exercise addicts,” struggle with them. A key to exercising is to overcome them.
The second way in which we can kind of help ourselves is to remember we evolved to be physically active for just two reasons (and this is what a lot of the book is about). We evolved to be physically active when it was necessary or socially rewarding. Most of our ancestors went out to hunt or gather every day because they would otherwise starve. The other times they were physically active was for fun pursuits like dancing or playing games and sports. These are fun things to do and have some social benefits. If we want to help ourselves exercise, we need to have that same mindset. Make it fun, but also make it necessary. One of the most important ways to make it necessary is to do it socially, like being part of a running group. The obligation makes it fun, social, and necessary.
The final anthropological approach that can help is not worrying about time and how much exercise you need. There is a myth that we evolved to be perpetually active, run marathons, and be so bulked up we can lift giant rocks with ease. The truth is far from that. Our ancestors were reasonably but not excessively active and strong. Typical-hunter gatherers engage in only about 2¼ hours a day of moderate to vigorous physical activity. They aren’t extremely muscular, and they sit as much as we do, nearly 10 hours a day. Further, a little bit of physical activity is enormously salubrious. Dose response curves show that just 150 minutes of exercise a week — only 21 minutes a day — lowers mortality rates by about 50 percent. Knowing that, I think, can help people feel better about doing just a little exercise instead of none.